Wireless power transfer is expected to become increasingly popular, for instance for wireless battery charging of mobile devices such as, for instance, mobile terminals, tablet computers, laptop computers, cameras, audio players, rechargeable toothbrushes, wireless headsets, as well as various other consumer products and appliances.
The Wireless Power Consortium has developed a wireless power transfer standard known as Qi. Other known wireless power transfer approaches include Alliance for Wireless Power, and Power Matters Alliance.
The wireless power transfer standard known as Qi by the Wireless Power Consortium will be referred to, without limitation, throughout this document as the presently preferred wireless power transfer manner applicable to the present invention. However, the invention may generally be applied also to other wireless power transfer standards or approaches, including but not limited to the ones mentioned above. Also, this disclosure is not limited to any particular power range but includes, without limitation, low power applications as well as medium power applications and high power applications.
Operation of devices that comply with Qi relies on magnetic induction between planar coils. Two kinds of devices are involved, namely devices that provide wireless power (referred to as base stations), and devices that consume wireless power (referred to as mobile devices). Power transfer takes place from a base station to a mobile device. For this purpose, a base station contains a subsystem (a power transmitter) that comprises a primary coil, whereas a mobile device contains a subsystem (a power receiver) that comprises a secondary coil. In operation, the primary coil and the secondary coil will constitute the two halves of a coreless resonant transformer.
Typically, a base station has a flat surface, on top of which a user can place one or more mobile devices so as to enjoy wireless battery charging or operational power supply for the mobile device(s) placed on the base station.
As with most electric power applications, there is a need to test the devices involved in wireless power transfer. There are several reasons why testing is important; regulatory requirements, manufacturer liability and market competition are a few examples.
In wireless power transfer, there is a desire to measure the energy received by the mobile device in order to assess the capability of the wireless power transmitter device 20 to deliver wireless power according to a given rating, criterion or standard, and/or to verify compliance with an applicable wireless power transfer standard.
Also, it is desired to test the communication between the transmitter (base station) and receiver (mobile device). In, for instance, Qi Medium Power, the wireless power transfer is controlled by way of complex handshaking and signaling between the devices, i.e. a bidirectional communication between the devices. In, for instance, Qi Low Power, there is a unidirectional communication where the receiver (mobile device) sends control messages to the transmitter (base station).
Moreover, there is a desire to evaluate the thermal exposure of a mobile device when being subjected to wireless power transfer from a wireless power transmitter. This is because during operation, heat will be generated by magnetic induction in the secondary coil of the power receiver, i.e. in the mobile device. Also, the power transmitter in the base station will generate heat that will be conveyed from the base station to the mobile device. If the thermal exposure for the mobile device becomes excessive, several undesired effects may arise. For instance, vital components may be damaged in the mobile device, such as for instance a lithium ion battery or electronic circuitry in a smartphone. At severe overheating, objects in the vicinity of the mobile device may be damaged and even cause a fire or toxic smoke hazard. Furthermore, the duration of the charging period may be prolonged, since protective circuitry in the mobile device may intervene to reduce or even suspend the charging power until the temperature has been reduced again.
Base stations can be tested by the provision of respective testing devices which comprise a wireless power receiver coil that matches the wireless power transmitter coil of the base station to be tested. By placing such a testing device on or otherwise adjacent to the base station and connecting the testing device to a host device, the host device may run various wireless power transfer tests by driving the wireless power receiver coil in a manner which mimics the indented operation of a mobile device from the base station's perspective, By monitoring the resulting behavior of the testing device, the host device may evaluate the performance of the base station and also identify potentially abnormal behavior of the base station. Since there are several different types of wireless power coils on the market, several different types of testing devices may also be required.
However, to perform these tests accurately, the host device needs to know certain information about the wireless power receiver coil. Such information can be hard-coded into the test session program run by the host device, or retrieved from a settings file or database at runtime. Alternatively, it may be entered manually by a test operator before or during the execution of the test session program.
The present inventor has identified problems and shortcomings with these approaches, since they are potentially error-prone and complicated. Relevant information about the wireless power receiver coil may be missing or incorrect. Manual approaches may be subject to errors in data entry. Also, there is a risk of mixing up different instances of testing devices, such that a test operator may intend to connect a certain testing device (having a certain specific type of wireless power receiver coil) in order to run tests on that receiver coil, but inadvertently connects another testing device (having another specific type of wireless power receiver coil) to the host device. The outcome of the test session will therefore be unreliable, misleading or even dangerous.
Hence, there is an expected need among different interest groups to be able to perform improved tests of wireless power transfer, taking the problems and shortcomings listed above into account. Such interest groups may for instance involve any of the following: developers, manufacturers or suppliers of wireless power transmitter devices; test or compliance entities in the field of wireless power transfer; and test or compliance entities in the field of consumer product safety.